Incomplete Dominance Research Articles

Genetics of the fuzzless ovule phenotype of Gossypium arboreum accession PI 615733 (cv. Zi-Hua Guang Zi)

Abstract Lint and fuzz are the two types of fiber that develop on cotton seeds. Lint is an economically important fiber used in the textile industry. Fuzz fibers remain attached to seeds, and reducing the amount of fuzz could improve ginning efficiency. The Gossypium arboreum accession PI 615733 from the United States Department of Agriculture cotton germplasm collection showed the fuzzless trait, where no fuzz fibers were observed on seeds. Accession PI 615733 was crossed with the fuzzy seeded G. arboreum accession PI 529729 to develop an F2 population. Seeds from F1 plants showed no fuzz fiber. For the F2 population of 409 plants, 239 plants were classified as fuzzless and 170 were classified as fuzzy. These data support a two-gene model with incomplete dominance. A greater understanding of the genetic mechanisms controlling fiber development on cotton seeds could contribute to breeding efforts to improve lint fiber yields and quality.

Association of chronic wasting disease susceptibility with prion protein variation in white-tailed deer (Odocoileus virginianus)

ABSTRACT Chronic wasting disease (CWD) is caused by prions, infectious proteinaceous particles, PrPCWD. We sequenced the PRNP gene of 2,899 white-tailed deer (WTD) from Illinois and southern Wisconsin, finding 38 haplotypes. Haplotypes A, B, D, E, G and 10 others encoded Q95G96S100N103A123Q226, designated ‘PrP variant A.’ Haplotype C and five other haplotypes encoded PrP ‘variant C’ (Q95S96S100N103A123Q226). Haplotype F and three other haplotypes encoded PrP ‘variant F’ (H95G96S100N103A123Q226). The association of CWD with encoded PrP variants was examined in 2,537 tested WTD from counties with CWD. Relative to PrP variant A, CWD susceptibility was lower in deer with PrP variant C (OR = 0.26, p < 0.001), and even lower in deer with PrP variant F (OR = 0.10, p < 0.0001). Susceptibility to CWD was highest in deer with both chromosomes encoding PrP variant A, lower with one copy encoding PrP variant A (OR = 0.25, p < 0.0001) and lowest in deer without PrP variant A (OR = 0.07, p < 0.0001). There appeared to be incomplete dominance for haplotypes encoding PrP variant C in reducing CWD susceptibility. Deer with both chromosomes encoding PrP variant F (FF) or one encoding PrP variant C and the other F (CF) were all CWD negative. Our results suggest that an increased population frequency of PrP variants C or F and a reduced frequency of PrP variant A may reduce the risk of CWD infection. Understanding the population and geographic distribution of PRNP polymorphisms may be a useful tool in CWD management.

Genotypic divergence in mouse oocyte transcriptomes: possible pathways to hybrid vigor impacting fertility and embryogenesis.

What causes hybrid vigor phenotypes in mammalian oocytes and preimplantation embryos? Answering this question should provide new insight into determinants of oocyte and embryo quality and infertility. Hybrid vigor could arise through a variety of mechanisms, many of which must operate through posttranscriptional mechanisms affecting oocyte mRNA accumulation, stability, translation, and degradation. The differential regulation of such mRNAs may impact essential pathways and functions within the oocyte. We conducted in-depth transcriptome comparisons of immature and mature oocytes of C57BL/6J and DBA/2J inbred strains and C57BL/6J × DBA/2J F1 (BDF1) hybrid oocytes with RNA sequencing, combined with novel computational methods of analysis. We observed extensive differences in mRNA expression and regulation between parental inbred strains and between inbred and hybrid genotypes, including mRNAs encoding proposed markers of oocyte quality. Unique BDF1 oocyte characteristics arise through a combination of additive dominance and incomplete dominance features in the transcriptome, with a lesser degree of transgressive mRNA expression. Special features of the BDF1 transcriptome most prominently relate to histone expression, mitochondrial function, and oxidative phosphorylation. The study reveals the major underlying mechanisms that contribute to superior properties of hybrid oocytes in a mouse model.

Mapping Cucumber Vein Yellowing Virus Resistance in Cucumber (Cucumis sativus L.) by Using BSA-seq Analysis.

Cucumber vein yellowing virus (CVYV) causes severe yield losses in cucurbit crops across Mediterranean countries. The control of this virus is based on cultural practices to prevent the presence of its vector (Bemisia tabaci) and breeding for natural resistance, which requires the identification of the loci involved and the development of molecular markers for linkage analysis. In this work, we mapped a monogenic locus for resistance to CVYV in cucumber by using a Bulked Segregant Analysis (BSA) strategy coupled with whole-genome resequencing. We phenotyped 135 F3 families from a segregating population between a susceptible pickling cucumber and a resistant Long Dutch type cucumber for CVYV resistance. Phenotypic analysis determined the monogenic and incomplete dominance inheritance of the resistance. We named the locus CsCvy-1. For mapping this locus, 15 resistant and 15 susceptible homozygous F2 individuals were selected for whole genome resequencing. By using a customized bioinformatics pipeline, we identified a unique region in chromosome 5 associated to resistance to CVYV, explaining more than 80% of the variability. The resequencing data provided us with additional SNP markers to decrease the interval of CsCvy-1 to 625 kb, containing 24 annotated genes. Markers flanking CsCvy-1 in a 5.3 cM interval were developed for marker-assisted selection (MAS) in breeding programs and will be useful for the identification of the target gene in future studies.

Combined effects of dosage compensation and incomplete dominance on gene expression in triploid cyprinids.

Hybridization and polyploidy are pervasive evolutionary features of flowering plants and frequent among some animal groups, such as fish. These processes always lead to novel genotypes and various phenotypes, including growth heterosis. However, its genetic basis in lower vertebrate is still poorly understood. Here, we conducted transcriptome-level analyses of the allopolyploid complex of Carassius auratus red var. (R) (♀) × Cyprinus carpio L. (C) (♂), including the allodiploid and allotetraploid with symmetric subgenomes, and the two allotriploids with asymmetric subgenomes. The gradual changes of gene silencing and novel gene expression suggested the weakening of the constraint of polymorphic expression in genotypic changes. Then, analyses of the direction and magnitude of homoeolog expression exhibited various asymmetric expression patterns, which supported that R incomplete dominance and dosage compensation were co-regulated in the two triploids. Under these effects, various magnitudes of R-homoeolog expression bias were observed in growth-regulated genes, suggesting that they might contribute to growth heterosis in the two triploids. The determination of R incomplete dominance and dosage compensation, which might be led by asymmetric subgenomes and multiple sets of homologous chromosomes, explained why various expression patterns were shaped and their potential contribution to growth heterosis in the two triploids.

Genetically inherited tolerance may unveil trait dominance patterns in an amphibian model

Chemical contamination may cause genetic erosion in natural populations by wiping out the most sensitive genotypes. This is of upmost concern if the loss of genetic variability is irreversible due to contaminant-driven elimination of alleles, which may happen if tolerance is a recessive or incompletely dominant trait – the recessive tolerance inheritance (working-) hypothesis. Accordingly, this work investigated the tolerance inheritance to lethal levels of a metal-rich acid mine drainage (AMD) and to copper sulphate in a population of Pelophylax perezi. Time-to-death for each egg, after being exposed to 60% of a sample of acid mine drainage and to 9 mg/L Cu, was registered, and, for each egg mass, the median lethal time (LT50) and respective quartiles (LT25 and LT75) were computed. Results suggested that genetically determined tolerance could be probably driven by incomplete dominance (with possible maternal effect influence), preliminarily supporting the initial hypothesis.

Identification of two novel COL10A1 heterozygous mutations in two Chinese pedigrees with Schmid-type metaphyseal chondrodysplasia

BackgroundSchmid-type metaphyseal chondrodysplasia (MCDS) is an autosomal dominant disorder caused by COL10A1 mutations, which is characterized by short stature, waddling gait, coxa vara and bowing of the long bones. However, descriptions of the expressivity of MCDS are rare.MethodsTwo probands and available family members affected with MCDS were subjected to clinical and radiological examination. Genomic DNA of all affected individuals was subjected to whole-exome sequencing, and candidate mutations were verified by Sanger sequencing in all available family members and in 250 healthy donors. A spatial model of the type X collagen (α1) C-terminal noncollagenous (NC1) domain was further constructed.ResultsWe found that the phenotype of affected family members exhibited incomplete dominance. Mutation analysis indicated that there were two novel heterozygous missense mutations, [c.1765 T > A (p.Phe589Ile)] and [c.1846A > G (p.Lys616Glu)] in the COL10A1 gene in family 1 and 2, respectively. The two novel substitution sites were highly conserved and the mutations were predicted to be deleterious by in silico analysis. Furthermore, protein modeling revealed that the two substitutions were located in the NC1 domain of collagen X (α1), which potentially impacted the trimerization of collagen X (α1) and combination with molecules in the pericellular matrix.ConclusionTwo novel mutations were identified in the present study, which will facilitate diagnosis of MCDS and further expand the spectrum of the COL10A1 mutations associated with MCDS patients. In addition, our research revealed the phenomenon of incomplete dominance in MCDS.

Modificación Diluída de Colores en Ovinos Shetland y Ouessant

Ovinos de la raza Shetland mostraban vellones de varios colores, los cuales variaban de oscuro a claro en un grupo basado en el negro (negro, negro cálido, café oscuro, y estaño) y otro basado en café (café, café claro, miel). Los ovinos produjeron 257 crias. Entre los colores mas diluidos, apareamientos de miel con miel solamente produjeron crias de color miel. Parejas estaño por estaño solamente produjeron crias de miel o estaño. Estos dos colores diluidos apereados con colores más oscuros, produjeron varios colores que concuerdan con un sistema de dos loci. En el cual el negro es dominante sobre el café en un locus (B), y los colores diluidos fueron recesivos respectos a los colores completamente intensos en un segundo locus (Mod que significa Modificado). Ambos loci tienen algún grado de dominancia incompleta, que representa la gama completa de colores de vellóon. Los resultados de la raza Ouessant incluyeron 41 crías, todos de colores del grupo basado en el negro. Los resultados de Ouessant son similares a ellos de Shetland, e indican que el mecanismo para la dilución del color de los vellones ocurre en varias razas.

АНАЛИЗ ИДЕНТИЧНОСТИ ГЕНОВ УСТОЙЧИВОСТИ К РАСЕ G ЗАРАЗИХИ У НЕКОТОРЫХ ЛИНИЙ ПОДСОЛНЕЧНИКА В F1

In the past few decades, the race formation of broomrape, a harmful obligate parasite of sunflower, has been increasing due to noncompliance with crop rotation standards. Over the course of several years, a number of inbreeding lines of various origin have been developed. They showed immunity to one of the last broomrape races, race G. The resistance control in these lines is monogenic with incomplete dominance. To be able to combine different genes in one sunflower genotype it is necessary to determine the allelism of resistance genes in the developed lines. Material and methods The sunflower lines served as the research material; it were the donors of resistance to the broomrape race G: RG, RGP1, RGP2, RGВ, RGL1, RGL2, RGM. The seeds of the broomrape race G were collected in the fields of Bokovsky and Morosovsky districts of the Rostov region. Seven hybrids of first generation from crossbreeding lines with each other were obtained in greenhouse and in the artificial climate chamber Biotron-5. Forced self-pollination was carried out by the method customary in VNIIMK, using individual spunbond insulators. Hybridization was conducted by means of manual castration. The plants were tested in the greenhouse for resistance and susceptibility to broomrape, using the early diagnosis method of A.Ya. Panchenko. Results As a result of the research, it was found that the manifestation of the resistance trait in F 1 plants is the same as in their parent forms. This type of inheritance of resistance in F 1 , that is, the manifestation of the trait as in both parents, is typical for lines with an identical gene. However, the presence of two different dominant resistance genes would show the same result in the first generation. Since the resistance trait is dominant in the studied lines, the analysis of F 2 progeny will allow to confirm is the resistance gene identical or not for the lines RG with RGP1, RG with RGM, RG with RGL1, RG with RGB, RGP2 with RGL2, RGM with RGL1, RGB with RGL1.

Genetic analysis of oleic acid content in the oils of maize sugary-2 mutants

Aim. Genetic analysis of oleate content in the carriers of maize mutation su2. Methods. Experiments were performed on a series of unrelated inbreeds – carriers of mutation su2 which were hybridized by the diallel and top – cross crossings. The analysis of the fatty acid composition of oil were carried out using a modified gas-chromatographic Peyskare method. Results. It was found, that su2 mutants were notable as having the increased content of oleate compared to the maize of usual type and this trait has a quantitative nature. The inbreeds – carriers of su2 mutation were significantly differed in the the effects of combining abilities for the oleate content. The inheritance of oleate was carried out by the type of incomplete dominance with the prevailing contribution of additive effects to the variance. Conclusions. In the sixth maize chromosome it is very likely that there is a spatial linkage of the su2 and oleate- encoding locus, the effect of which can be modified by the polygenic complex. Keywords: Zea mays L., mutation su2, oleic acid, genetic analysis.

Plyustransgression in winter wheat breeding on frost resistance and productivity

The results of breeding on the Don using transgressive variability during 1985 - 2018 are presented. The location is a chernozem steppe with frequent frosts, insufficient and unstable moistening over the years. The technology of breeding is common. Used pedigree and bulk method. New when laying a breeding nursery was sowing up to 45 thousand untreated ears of a designed planter (to eliminate weeding during threshing ears), determining the frost resistance of plants that have been hardened in the field, in bundles placed in plastic bags, in low temperatures, determining their viability for three days after freezing by the Don method. A large layer of studies ( more than 11,000 populations) was analyzed, starting with F1 and ending with the completion of formation for each. It is confirmed that transgression, the result of the recombination, is observed in populations whose parents do not have extreme severity of the trait. It is established that populations should be heterogeneous with long-term formation. This happens when parents have very few common genes, when there is no restriction on recombination due to too large differences in components. With the presence of overdominance in F1 in many studied populations, it is possible to predict the appearance of transgressions (in our case for frost-resistance and productivity) with an average frequency of 0.25-4.36%. With the incomplete and complete dominance of the trait of the best parent, the excess of parents in F2 on average over the population, intermediate inheritance in F2 traits are also possible, but an order of magnitude less than when overdominated. This should be accompanied by large volumes of study of the breeding material in the first stages and the pressure of stresses of various kinds. Of the 38 varieties that at various times included in the State Register of Russia, 29 were transgressive recombinants for winter hardiness and productivity. They all withstand minus 18⁰ С on the tillering knot

Gene Expression Profiling and Fine Mapping Identifies a Gibberellin 2-Oxidase Gene Co-segregating With the Dominant Dwarfing Gene Ddw1 in Rye (Secale cereale L.).

The gibberellin (GA)-sensitive dwarfing gene Ddw1 provides an opportunity to genetically reduce plant height in rye. Genetic analysis in a population of recombinant inbred lines confirmed a monogenetic dominant inheritance of Ddw1. Significant phenotypic differences in PH between homo- and heterozygotic genotypes indicate an incomplete dominance of Ddw1. De novo transcriptome sequencing of Ddw1 mutant as well as tall genotypes resulted in 113,547 contigs with an average length of 318 bp covering 36.18 Mbp rye DNA. A hierarchical cluster analysis based on individual groups of rye homologs of functionally characterized rice genes controlling morphological or physiological traits including plant height, flowering time, and source activity identified the gene expression profile of stems at the begin of heading to most comprehensively mirror effects of Ddw1. Genome-wide expression profiling identified 186 transcripts differentially expressed between semi-dwarf and tall genotypes in stems. In total, 29 novel markers have been established and mapped to a 27.2 cM segment in the distal part of the long arm of chromosome 5R. Ddw1 could be mapped within a 0.4 cM interval co-segregating with a marker representing the C20-GA2-oxidase gene ScGA2ox12, that is up-regulated in stems of Ddw1 genotypes. The increased expression of ScGA2ox12 observed in semi-dwarf rye as well as structural alterations in transcript sequences associated with the ScGA2ox12 gene implicate, that Ddw1 is a dominant gain-of-function mutant. Integration of the target interval in the wheat reference genome sequence indicated perfect micro-colinearity between the Ddw1 locus and a 831 kb segment on chromosome 5A, which resides inside of a 11.21 Mb interval carrying the GA-sensitive dwarfing gene Rht12 in wheat. The potential of Ddw1 as a breeder’s option to improve lodging tolerance in rye is discussed.

Genome-wide identification and analysis of heterotic loci in three maize hybrids.

SummaryHeterosis, or hybrid vigour, is a predominant phenomenon in plant genetics, serving as the basis of crop hybrid breeding, but the causative loci and genes underlying heterosis remain unclear in many crops. Here, we present a large‐scale genetic analysis using 5360 offsprings from three elite maize hybrids, which identifies 628 loci underlying 19 yield‐related traits with relatively high mapping resolutions. Heterotic pattern investigations of the 628 loci show that numerous loci, mostly with complete–incomplete dominance (the major one) or overdominance effects (the secondary one) for heterozygous genotypes and nearly equal proportion of advantageous alleles from both parental lines, are the major causes of strong heterosis in these hybrids. Follow‐up studies for 17 heterotic loci in an independent experiment using 2225 F2 individuals suggest most heterotic effects are roughly stable between environments with a small variation. Candidate gene analysis for one major heterotic locus (ub3) in maize implies that there may exist some common genes contributing to crop heterosis. These results provide a community resource for genetics studies in maize and new implications for heterosis in plants.

Wheat ms5 male-sterility is induced by recessive homoeologous A and D genome non-specific lipid transfer proteins.

Nuclear male-sterile mutants with non-conditional, recessive and strictly monogenic inheritance are useful for both hybrid and conventional breeding systems, and have long been a research focus for many crops. In allohexaploid wheat, however, genic redundancy results in rarity of such mutants, with the ethyl methanesulfonate-induced mutant ms5 among the few reported to date. Here, we identify TaMs5 as a glycosylphosphatidylinositol-anchored lipid transfer protein required for normal pollen exine development, and by transgenic complementation demonstrate that TaMs5-A restores fertility to ms5. We show ms5 locates to a centromere-proximal interval and has a sterility inheritance pattern modulated by TaMs5-D but not TaMs5-B. We describe two allelic forms of TaMs5-D, one of which is non-functional and confers mono-factorial inheritance of sterility. The second form is functional but shows incomplete dominance. Consistent with reduced functionality, transcript abundance in developing anthers was found to be lower for TaMs5-D than TaMs5-A. At the 3B homoeolocus, we found only non-functional alleles among 178 diverse hexaploid and tetraploid wheats that include landraces and Triticum dicoccoides. Apparent ubiquity of non-functional TaMs5-B alleles suggests loss-of-function arose early in wheat evolution and, therefore, at most knockout of two homoeoloci is required for sterility. This work provides genetic information, resources and tools required for successful implementation of ms5 sterility in breeding systems for bread and durum wheats.

Swede midge (Diptera: Cecidomyiidae) diapause initiation under stable conditions: not a family affair

AbstractLarvae of the swede midge,Contarinia nasturtii(Kieffer) (Diptera: Cecidomyiidae), rely on environmental cues to initiate the diapause programme. This facultative diapause strategy, which provides opportunities for both bet hedging and multivoltinism, likely contributed to the successful colonisation and spread of this invasive pest in North America. Population diapause incidence is variable even under relatively stable conditions (especially at the critical day length), yet the mechanisms influencing the developmental trajectory of individuals under such conditions are unknown. Here we approach the non-environmental (i.e., heritable) controls of this variation by comparing diapause frequencies within and among full-sibling swede midge families reared in one of two stable environments. Under warm, long-day conditions &amp;gt; 99% of swede midges pupated directly, while 86% of swede midges entered diapause under cool, short-day conditions. In the latter condition, most families exhibited mixed developmental trajectories (ranging from 36% to 96% diapause). This developmental variation among siblings indicates that the diapause induction threshold does not follow simple Mendelian inheritance with complete dominance for a particular allele, but may follow incomplete dominance or a more complex heredity. Alternatively, within-family diapause variation may result from maternal bet hedging or factors such as maternal age or larval nutrition.

Additive Traits Lead to Feeding Advantage and Reproductive Isolation, Promoting Homoploid Hybrid Speciation.

Speciation through homoploid hybridization (HHS) is considered extremely rare in animals. This is mainly because the establishment of reproductive isolation as a product of hybridization is uncommon. Additionally, many traits are underpinned by polygeny and/or incomplete dominance, where the hybrid phenotype is an additive blend of parental characteristics. Phenotypically intermediate hybrids are usually at a fitness disadvantage compared with parental species and tend to vanish through backcrossing with parental population(s). It is therefore unknown whether the additive nature of hybrid traits in itself could lead successfully to HHS. Using a multi-marker genetic data set and a meta-analysis of diet and morphology, we investigated a potential case of HHS in the prions (Pachyptila spp.), seabirds distinguished by their bills, prey choice, and timing of breeding. Using approximate Bayesian computation, we show that the medium-billed Salvin’s prion (Pachyptila salvini) could be a hybrid between the narrow-billed Antarctic prion (Pachyptila desolata) and broad-billed prion (Pachyptila vittata). Remarkably, P. salvini’s intermediate bill width has given it a feeding advantage with respect to the other Pachyptila species, allowing it to consume a broader range of prey, potentially increasing its fitness. Available metadata showed that P. salvini is also intermediate in breeding phenology and, with no overlap in breeding times, it is effectively reproductively isolated from either parental species through allochrony. These results provide evidence for a case of HHS in nature, and show for the first time that additivity of divergent parental traits alone can lead directly to increased hybrid fitness and reproductive isolation.

Sunflower Resistance to Race G of Broomrape (Orobanche Cumana Wallr.) In the Russian Federation: the Development of the Lines and the Study of Inheritance

Abstract The objective of this work is the development of sunflower lines that are not affected by race G of broomrape, as well as the determination of genetic control of resistance. The testing of the resistance of VNIIMK’s collection accessions of a cultivated sunflower of various origins was carried out on an artificial background made from the seeds of race G of broomrape. 6 lines resistant to race G were developed by the method of inbreeding on the basis of the obtained unaffected forms. The genetic control of resistance of one of them was studied. The resistance was inherited monogeneuosly, with incomplete dominance. There was established the presence of a reciprocal effect and the dependence of the resistance characteristic on the genotype of a susceptible parent under crossbreeding with certain lines. The other 5 sunflower lines are in the process of a hybridological analysis in order to determine the genetic control of their resistance. The combination of different genes of resistance to the same race of broomrape in one sunflower genotype could contribute to the long-term resistance of the crop to the parasite. The results of the presented study are of high importance for breeders, since the gene that we studied provides a new source of resistance to race G, thereby ensuring the protection of sunflower from the spread of new Orobanche pathotypes.

Genetic dissection of haploid male fertility in maize (Zea mays L.)

AbstractHaploid genome doubling is a key limiting step of haploid breeding in maize. Spontaneous restoration of haploid male fertility (HMF) provides a more promising method than the artificial doubling process. To reveal the genetic basis of HMF, haploids were obtained from the offspring of 285 F2:3 families, derived from the cross Zheng58 × K22. The F2:3 families were used as the female donor and Yu high inducer No. 1 (YHI‐1) as the male inducer line. The rates of HMF from each family line were evaluated at two field sites over two planting seasons. HMF displayed incomplete dominance. Transgressive segregation of haploids from F2:3 families was observed relative to haploids derived from the two parents of the mapping population. A total of nine quantitative trait loci (QTL) were detected, which were distributed on chromosomes 1, 3, 4, 7 and 8. Three major QTL, qHMF3b, qHMF7a and qHMF7b were detected in both locations, respectively. These QTL could be useful to predict the ability of spontaneous haploid genome doubling, and to accelerate the haploid breeding process by introgression or aggregation of those QTL.

CORRELATIONS BETWEEN FRUIT’S YIELD WITH HORTICULTURAL TRAITS AND INHERITANCE OF MORPHOLOGICAL TRAITS OF SPONGE GOURD (LUFFA CYLINDRICA)

Abstract: Enhancing the production yield fornew generations of each horticultural crop needseffective selecting programs to find outexcellent traits forming thisfruit yield. Therefore,this study aims to investigate the correlations between the fruit yield withhorticultural traits, mainly with yield’s components and inheritance of some morphological traitsofsponge gourd (Luffa cylindrica). An F2 population was generated from a cross between sponge gourds GBVN006904 (male) and GBVN005333 (female) at University of Agriculture and Forestry, Hue University,Vietnam. The positive correlations are observed between the fruit yield per plant andthe fruit diameter, fruit weight, and number of fruits per plant (0.901**). The male first flower appearance time showsa significant positive correlation with female first flower appearance one. The peduncle length correlates positively with the fruit length. The fruit length is enhanced when fruit weight increases. The total soluble solids and fruit diameter show a slightly negative correlation. Chi-square analysis for the leaf shape, depth of lobing, leaf color, and leaf pubescence shows a good fit to a ratio of 9:6:1, thus being controlled by duplicate genes interaction. The fruit color (dark-green:light-green) fits well to a ratio of 15:1, giving its control to duplicate genes with dark-green color being dominant, whereas the fruit shape assorts independently according toa ratio of 9:3:3:1. The fruit stripe color exhibits monogenic incomplete dominance, and the curvature of the fruit is a monogenic recessive trait. Fruit yield components, such as the number of fruit per plant, the fruit weight, and the fruit diameter,strongly affect the fruit yield of sponge gourd. The inheritance of morphological traits indicates that most of the traits are controlled by complete dominance at both gene pairs excepted for fruit strip color and curvature of fruit.Keywords: correlation, inheritance, morphological traits, sponge gourd, yield components

Ty-6, a major begomovirus resistance gene on chromosome 10, is effective against Tomato yellow leaf curl virus and Tomato mottle virus

Key messageTy-6 is a major resistance gene on chromosome 10 of tomato that provides resistance against monopartite and bipartite begomoviruses and complements resistance conferred by the known Ty-3 and ty-5 genes.Resistance to monopartite and bipartite begomoviruses is an important breeding objective for cultivated tomato. Several begomovirus resistance genes have been introgressed from related Solanum species and are available for breeding purposes. In the present study, we mapped an additional locus, Ty-6, to chromosome 10 of tomato. Ty-6 is effective against both monopartite Tomato yellow leaf curl virus (TYLCV) and bipartite Tomato mottle virus (ToMoV). Gene action is incomplete dominance, with an intermediate resistance response when Ty-6 is heterozygous. Analysis of populations segregating for Ty-6 along with Ty-3 or ty-5 indicates that the highest level of resistance against TYLCV is attained when Ty-6 is combined with an additional resistance allele. Our results also demonstrate that ty-5 is ineffective against ToMoV. Although multiple SNPs linked to Ty-6 were identified and can be used for breeding purposes, none of these were consistently polymorphic between Ty-6 and ty-6 breeding lines. Further research is underway to generate resequencing data for several Ty-6 inbred lines for the discovery of additional sequence polymorphisms that can be used for fine mapping and characterizing the Ty-6 locus.